This invention relates to a shock absorber construction and more particularly to an improved sealing piston ring arrangement for a shock absorber.
A common type of shock absorber used for suspension systems and other purposes employs a piston that is slidably supported within a hydraulic cylinder. The piston and/or cylinder are provided with passages that extend between opposite sides of the piston and which include an arrangement for damping the flow therethrough. This provides a hydraulic damping action, as is well known in the art.
With this type of arrangement, however, there is also provided a seal on the exterior surface of the piston which engages and seals with the cylinder so as to preclude fluid leakage past the seal that would permit fluid to bypass the damping arrangement mentioned. However, these types of arrangements provide certain problems, as may be best understood by reference to FIG. 1 which shows a conventional seal of the type utilized in shock absorbers.
FIG. 1 shows a portion of a shock absorber arrangement of the prior art type and this shock absorber mechanism is shown only partially and in cross-section to indicate the problems associated with the seal therein. The overall construction of the shock absorber in which the sealing mechanism is employed may be of any known type and such structures will be shown later in describing the preferred embodiment of the invention in FIG. 2.
Nevertheless, the shock absorber includes an outer cylinder 21 which defines a cylinder bore 22 in which a piston 23 reciprocates. The cylinder 22 is filled with hydraulic fluid so as to form chambers above and below the piston 23. In addition, flow passages are provided between the two chambers, normally in the body of the piston 23, through which fluid may flow in a damped fashion so as to damp the suspension movement with which the shock absorber is associated.
In order to provide a seal and insure against leakage around this shock absorbing passage arrangement, at least one piston ring groove 24 is formed in the outer peripheral surface of the piston 23. A piston ring 25 is provided in this piston ring groove 24. This piston ring 25 may be of any type of construction and is pressed by its own resilience and by that of an O-ring 26 into sealing engagement with the cylinder surface 22. The O-ring 26 is received in a groove 27 formed in the exterior surface of the piston 23 at the base of the ring groove 24.
As may be seen in this Figure, if the piston 23 is forced downwardly relative to the cylinder 21 in the direction indicated by the force arrow F, the piston ring 25 will slide slightly upwardly and bottom against the upper side of the ring groove 24 of the piston 23.
Thus, some fluid under pressure may enter into this area through a gap G that exists between the exterior surface of the piston 23 and the cylinder 22. This pressure can then flow into a further gap area G.sub.1 behind the piston ring 25.
Thus, a hydraulic pressure is exerted which acts in conjunction with the pressure of ring 25 and the O-ring 26 to force the piston ring 25 into tight engagement with the surface 22 of the cylinder 21. This restricts motion and can cause imprecise action of the shock absorber.
Arrangements have been proposed for reducing this effect by permitting a passage that will communicate the exterior surface of the piston ring with its interior surface. However, such passages then provide a path through which fluid may leak from one end of the piston ring to the other. Thus the shock absorbing system will be partially bypassed.
It is, therefore, a principal object of this invention to provide an improved piston ring arrangement that can be utilized with shock absorbers or other similar arrangements.
It is a further object of this invention to provide an improved piston ring arrangement wherein compressive pressure in one of the fluid chambers defined by the associated piston will not act on the piston ring to vary its sealing force with the cylinder in which it is received.